1. Field of the Invention
The present invention relates to a post-processing apparatus and an image forming system using the same.
2. Description of Related Art
Recently, in an art of production printing, an image forming system has been widely used in which any various systems can be structured by connecting an image forming apparatus with any peripheral equipment such as a large capacity sheet feeder and the post-processing apparatus. The post-processing apparatus includes, for example, bookbinding equipment that binds a booklet by performing any center-folding processing or saddle stitching processing on sheets of paper on each of which the image forming apparatus forms an image. The post-processing apparatus also includes other equipment that performs a stapling processing or punching processing.
When performing the saddle stitching processing as the post processing, if plural saddle-stitching-processed booklets are stacked on, for example, a table, they may collapse because of their curved ends (herein after, referred to as “back portions”) in each of which a fold is formed. Further, there may be an issue where they are bulgy in their back portions when storing and carrying the booklets. Accordingly, when performing the saddle stitching processing, any flattening processing for flattening the back portion of each booklet so as to form a sectionally angular shape (square back processing) has been performed by applying any pressure on the curved portion of the back portion of each booklet to flatten the back portion of each booklet.
Japanese Patent Application Publication No. 2009-227449 discloses recording material post-processing device that has a constraint means for constraining the neighborhood of the spine of the booklet in which the bundle of recording materials is folded at the center and arranging the spine of the booklet to protrude from a booklet constrain position. This device also has a pressing means for pressing the spine of booklet constrained by the constraining means to form a flat spine surface from the curved spine surface.
Japanese Patent Application Publication No. 2010-265115 discloses a spine forming apparatus which has a pair of conveying rollers that conveys a bundle of sheets folded in half with a curved folded portion of the bundle of sheets directing forward, pressing means for pressing and nipping the forward end of the bundle of sheets and spine forming means for forming the spine by flattening the curved folded portion. The pressing means includes first pressing members and second pressing members for nipping the bundle of sheets operating together with the pressing operation of the first pressing members and applies a spine forming load onto the folded portion of the bundle of sheets.
Japanese Patent Application Publication No. 2010-036403 discloses a booklet-forming apparatus that flattens a back of the conveying booklet by rotating a pair of first pressing and conveying rollers around a shaft while nipping the booklet and conveying the booklet along a first guide portion while the back of the booklet is pressed on the first guide portion.